A clinical trial conducted by the University of Chicago in the early 1950's produced a cohort of infants exposed to the synthetic estrogen DES in utero, and a similar group of unexposed infants. Those individuals are now in their late thirties and constitute an important resource for epidemiologic studies of DES effects. Previous studies of this cohort have shown evidence of reproductive impairment of the daughters, but similar studies of the sons have not been done. The purposes of the present project are: 1. To collect prospective data on the menstrual function of the daughters. Menstruation is a function of the endocrine cycle of the female. DES is known to affect the structure of reproductive organs, but its effect on endocrine function has not been shown. A close look at menstrual patterns will be a first step in identifying possible hormonal dysfunction in humans secondary to DES exposure. 2. To collect data on the reproductive capacity of sons exposed to DES. This will be the first study to describe reproductive impairments (if any) among the sons of mothers who received DES during pregnancy. 3. To explore selected hypotheses of biological differences attributable to prenatal exposure to estrogen.